Emergency personnel were standing by when the plane, a Boeing 777, made its unexpected landing. The airline helped passengers make other travel arrangements.

"As a precautionary measure, Flight 58 from Houston to Amsterdam returned to IAH because the crew identified an issue with one of the engines," United said in a prepared statement. "The Boeing 777 aircraft, which was carrying 223 passengers and 15 crewmembers, landed safely and without incident in Houston at 5:13 p.m. Our maintenance team will review the aircraft, and we are re-accommodating all the customers on an alternative airplane."

United did not specify the nature of the engine problem. Other news reports said the engine shut off in mid-flight.

Flight 58 had a scheduled departure time of 3:35 p.m. It was not immediately known when it took off Thursday.